The present invention relates to an image forming apparatus having a sheet transport path extending substantially vertically upward from a sheet feed section to a sheet discharge section via an image forming section. More particularly, the present invention is concerned with a printer, facsimile apparatus or similar image forming apparatus allowing a sorter, sorter/stapler, mail box or similar finisher t o be readily mounted thereto.
A multifunction image forming apparatus selectively operable as, e.g., a copier, printer or facsimile apparatus is extensively used today. This kind of apparatus has customarily been provided with a construction based on a copier. Therefore, to use the apparatus as a printer, peripherals for use with the apparatus have each been provided with a mechanism for turning over sheets sequentially output in the order of page. However, the remarkable spread of personal computers is substituting a printer-based configuration for the traditional copier-based configuration. An image forming apparatus based on a printer is so constructed as to discharge a sheet carrying an image thereon via a sheet discharge section face down by way of a substantially vertically extending sheet transport path. Specifically, the printer-based apparatus has a sheet feed section and the sheet discharge section below and above an image forming section, respectively. The sheet transport path extends substantially vertically from the sheet feed section to the sheet discharge section. While a sheet is conveyed along such a transport path, a toner image is transferred to the sheet. The sheet with the toner image is driven out of the apparatus face down via the sheet discharge section. The substantially vertical transport path is far shorter than the conventional sheet transport path, noticeably reducing the interval between the sheet feed and the sheet discharge. In addition, this path can be almost fully exposed to the outside only if one side of the apparatus is opened, insuring sheet transport and promoting easy removal of a jamming sheet.
However, some problems arise when a sorter, sorter/stapler, mail box or similar finisher is mounted to the apparatus having the substantially vertical transport path. The apparatus has a sheet outlet in its upper portion. Therefore, when a mail box, for example, is mounted to the apparatus, it increases the overall height of the apparatus, and therefore raises the level of a scanner and that of an operation panel, obstructing easy operation. Moreover, mounting a mail box having a number of trays is impractical because the overall height of the apparatus is naturally limited in relation to maneuvability. In addition, the apparatus needs a mechanical strength great enough to bear the weight of the mail box, resulting in an increase in cost.
As stated above, the advantages particular to the substantially vertical transport path cannot be utilized when the above finisher is mounted to the apparatus.
When the finisher is mounted to an image forming apparatus, whether it be provided with the substantially vertical transport path or not, a conveying device for conveying a sheet driven out via the sheet discharge section of the apparatus to the finisher must be mounted to the apparatus. This cannot be done without resorting to exclusive parts and time- and labor-consuming work for mounting the conveying device to the apparatus. In addition, the conveying device increases the number of parts and cost.
There is an increasing demand for an image forming apparatus with a substantially vertical sheet transport path and allowing a plurality of finishers mounted thereto at the same time. However, it is difficult for a plurality of finishers to coexist on a single image forming apparatus. For example, mounting a mail box on the top of the apparatus while mounting a sorter/stapler on the side of the same is not easy. In light of the above, a relay unit having its own sheet transport path and sheet conveying function may be located at the upper portion of the apparatus. The relay unit connects the sheet discharge section to, e.g., a sorter/stapler mounted on the side of the apparatus which does not interfere with, e.g., a mail box mounted on the top of the apparatus. The conveying function as well as a path selecting function available with the relay unit allows the sorter/stapler and mail box to exist together on a single apparatus.
However, the problem with the relay unit is that a sheet jam is apt to occur thereinside due to its own transport path and conveying function. To obviate this kind of sheet jam, the relay unit includes a rotatable cover which may be opened in order to remove a jamming sheet. A portion for effecting usual sheet discharge is constructed integrally with the upstream side of the relay unit. A rotatable cover is also provided in this portion for the removal of a jamming sheet.
The prerequisite with the relay unit is that it be positioned close to the trays of the mail box in order to avoid a noticeable increase in the overall dimensions of the apparatus. This brings about a drawback that when any one of the covers is opened for removing a jamming sheet, the trays of the mail box limit the space available for the removal of the sheet. On the other hand, when an image reading device is mounted o n the top of the apparatus, it must be positioned right above the relay unit so as not to raise the level of the operation surface of the device as far as possible. This also makes it difficult to remove a jamming sheet by hand.